The film stars the voices of Amy Poehler, Phyllis Smith, Richard Kind, Bill Hader, Lewis Black, Mindy Kaling, Kaitlyn Dias, Diane Lane, and Kyle MacLachlan.

The project was subsequently green-lit, and Docter and co-director Ronnie del Carmen developed the story, while consulting psychologists and neuroscientists in an effort to accurately portray the mind.

It received critical acclaim for its craftsmanship, screenplay, subject matter, plot, and vocal performances—particularly those of Poehler, Smith, Kind, Hader, Kaling, and Black.

In the absence of Joy and Sadness, Anger, Fear, and Disgust try to make happy core memories, but the results are disastrous, distancing Riley from her parents, peers, and hobbies.

While navigating the vast long-term memory area, Joy and Sadness encounter Bing Bong, Riley's imaginary friend, who suggests riding the "train of thought" back to Headquarters.

Development of Inside Out was green-lit in October 2009,[1] after director Pete Docter noticed his daughter Elie becoming "more quiet and reserved",[2] and began to wonder what was happening internally.

[1] According to Keltner and Ekman, the film emphasizes the ways emotions organize our thoughts and social lives, especially the role of sadness in fostering connections.

[10] About 27 emotions—including irritation, envy, greed, gloom, despair, depression, love, schadenfreude, ennui, shame, embarrassment, and hope—were considered for early versions of the film, but the number was later reduced for the sake of simplicity.

[24] Del Carmen described his upbringing as a significant influence and had the idea of making Riley an avid ice-hockey player due to that sport's popularity in Minnesota.

[25][26] Though the film's script was deemed ambitious and ingenious, screenwriter Michael Arndt spent a year on it before leaving the project in early 2011;[27] he was attributed with providing additional story material.

[2] Creation of storyboards for Inside Out took two-to-three years and included seven-to-eight screenings for Pixar's "brains trust", a small group of creative leaders who oversee development of all films.

[34] In one instance, Riley was to have wanted the lead role as a turkey in a Thanksgiving Day pageant; Docter found that plot idea to be too unfamiliar and sought something to replace it.

Docter deemed this problematic and determined the idea about Joy had learned from Fear to develop her characterization, before deciding to integrate emotions and relationships within the film.

[19] The worlds' design resembles those of Pixar films Up and Toy Story 3 (2010),[16] the romantic drama One from the Heart (1982), David Hockney's theatrical productions,[53] and the intended 1950s Broadway musicals.

About 48 animators, including supervisors Shawn Krause and Victor Navone, and director Jamie Roe and 350 artists—35 of them lighting–led by cinematographer Kim White–and 10 layout—and technicians were involved in the production.

[1] Inside Out made increased use of an advanced sketching tool with which animators performed rapid sculpting on silhouettes, altering the characters' appearances and evaluating a "fine-tuning" cloth stimulation.

[11] Pixar co-founder Edwin Catmull felt the characters' attributes have to a lesser extent humanoid forms, bright colors, and strange shapes due to their possession of force fields.

[19][66] Inside Out's certain aspects were supported by "scale progressions" (the worldbuilding size based on the main characters' perspective) for characterizations, as well as Riley and Joy's arcs, staging for the story, and framing for the theme.

[71] Disney's marketing strategy included an active social media campaign,[72] a worldwide publicity tour,[73] and the creation of five colorful character posters.

[103] Inside Out's successful opening was attributed to its Cannes premiere, CinemaCon, and Fathom Events screenings, favorable critical reception and word-of-mouth, and its release over the Father's Day weekend.

[119] Deadline Hollywood calculated the film's net profit as $279.51 million, accounting for production budgets, marketing, talent participation, and other costs; box-office grosses and home-media revenues placed it sixth on their list of 2015's "Most Valuable Blockbusters".

[104] Before Inside Out's release, fans and critics were concerned by a perceived over-dependence on sequels on the part of Pixar that was exacerbated by the announcement of Toy Story 4 (2019), and their films' decline in quality.

[147] Despite these overall reviews, The Guardian critic Peter Bradshaw and Slant Magazine writer Christopher Gray assessed the film as slightly inferior to Pixar's best works.

[156] Rene Rodriguez, writing for the Miami Herald, said the story skips from the beginning to the end and characters inside Riley's head have thin goals.

[177] Natasha Moore of the Australian ABC News said of the film's theme: "[If] Riley's carefree life gets more complicated, ... Joy's attempts to deliver uninterrupted happiness become increasingly neurotic".

[180] Ruth Bettelheim of USA Today wrote human responses to physical and social environments evolved over millions of years and are yet fully understood, as shown by the film's omission of Riley's bodily sensations and their possible effect on mental states.

Primatologist Louise Barrett said the film shows disconnection between characters who are not relating to each other or to their own emotions but moments of personal harmony lead to positive interpersonal connections.

[181] According to USA Today's Jamie Altman, Inside Out shows major environmental changes can be "difficult, but not impossible, to overcome", recommending it to college students experiencing homesickness or sadness.

Pediatrician Denise Daniels sued Disney and Pixar in 2017, claiming the film's personified emotions infringed on her pitch for a television series called The Moodsters.

[213] It featured Docter's "five to 27 emotions" idea,[12] incorporating Anxiety (Maya Hawke), Envy (Ayo Edebiri), Embarrassment (Paul Walter Hauser), Ennui (Adèle Exarchopoulos), and Nostalgia (June Squibb) into the sequel,[214] and outgrossed the original film at the box office.